Eu usei esse código antes dos asserts(comente todos os asserts do chainparams.cpp):

arith_uint256 best = arith_uint256();
   int n=0;
   arith_uint256 hashTarget = arith_uint256().SetCompact(genesis.nBits);
   while (UintToArith256(genesis.GetHash()) > hashTarget) {
     arith_uint256 c=UintToArith256(genesis.GetHash());
               
     if(c < best || n==0)
       {
         best = c;
         n=1;
         printf("%s %s %s\n",genesis.GetHash().GetHex().c_str(),hashTarget.GetHex().c_str(),
           best.GetHex().c_str());
       }
    
     ++genesis.nNonce;
     if (genesis.nNonce == 0) { ++genesis.nTime; }
   }
   printf("%s\n",genesis.ToString().c_str());